Zinc base alloy



Patented July 21-, 1931 -UNITED STATES PATENT OFFICE PASCAL J. MORELL,OF WATERBURY, CONNECTICUT, ASSIGNOR TO THE AMERICAN BRASS COMPANY, OFWATERBURY, CONNECTICUT, A CORPORATION OF CONNEC'ILIC'U'J;

ZINC BASE ALLOY Ho Drawing. Application filed June 18,

This invention relates to zinc base alloys, and more particularl to suchalloys for die casting andthelike. it the present time zinc base alloyssuitable for die casting and known and in extensive use, and underfavorable conditions have a comparatively high tensile strength,relatively high impact strength and fair ductility. A zinc base diecasting alloy commonly in use at the resent time contains about 4%aluminum, abofit 3% copper, about 0.1% magnesium,- and the balance zinc.It is widely used in the die casting industry. Tests have shown,however, that the strength of this alloy, like all other known zinc basealloys, decreases with time after casting. The decrease in physicalproperties is particular- 1y marked it the cast alloy is heated in theresence of water vapor. This and other rnown zinc base alloys aresubject to. a certain inter-crystalline oxidation or corrosion in thepresence of warmth and moisture, causing swelling, warping and loss ofstrength. Still further, changes occur, in these alloys upon ageing atthe ordinary temperatures unaccompanied by serious inter-crystallineoxidation, which changes may result in serious loss or decrease ofcertain physical properties of the alloy, such as tensile and im actstrength,

t is, therefore, an object of this invention to'produce an improved zincbase alloy which is adapted to be cast in permanent and sand molds, andis also especially adapted for die casting. A particular object is toproduce an improved alloy which. is not subject to intercrystallinecorrosion or at least in which this corrosion is greatly decreased, andespecially in which the corrosion attack in the presence of moisture andheat is greatly decreased and practically eliminated.

It is also an ob'ect of the invention to produce an alloy 1n whichdeterioration in strength is less than in the known alloys, and

in which the change in physical properties as measured by tensilestrength, elongation and im act value is small, thus making itparticular yyaluable "for die casting and similar purposes.

The invention involves the addition of a 1930. Serial No. 462,141.

small amounts to zinc base alloysand more particularly to a zinc basealloy containing copper. I have found that silicon when added to zincbase copper alloys produces an alloy which is very resistant todeterioration by corrosion even under adverse conditions of heat andmoisture, and furthermore, produces an alloy which is not subject toundosirable changes in physical properties or to structural orequilibrium changes.

Silicon can be used alone with the zinc and copper or in combinationwith any of the following metals such as manganese, magnesium, nickel,iron, cobalt or chromium. The silicon alone has a hardening eflect andgives improved physical properties to the zinc base copper alloy, but itis desirable under certain conditions in addition to silicon to add oneor more of the other metals to the zinc base copper alloy. Zinc basealloys containing copper, particularly from about 1 to about 15percentof copper, are greatly improved by the presence of silicon -fromapproximately .005 to about 5%, and the alloy may be further improved bythe addition of small amounts of magnesium, manganese, nickel, iron,cobalt or chromium as further described. Such alloys have high tensilestrength and are much less subject to corrosion, and particularly aremore resistant to corrosion in the presence of warmth and moisture thanheretofore known zinc base alloys. Furthermore, ageing or deteriorationin physical properties. such as tensile and impact strength whenunaccompanied by corrosion, is much less in these alloys.

A further reason for adding. magnesium is its efiect in reducing oreliminating the deleterious eii'ect of impurities such as lead which maybe present in commercial grades of zinc.

The presence of aluminum is of further advantage if the alloy is to beused for die casting due to its action in preventin the atcopper andrelatively small amounts of silihardener such as silicon inconclparatively con. To these alloys may be added any of 3p the othermetals above mentioned. The silicon is preferably from about .08 toabout .15%, but may vary from about .005 to about 5%. \Vhen aluminum isadded it is preferably from about .25 to about 35%, but may vary fromabout .005 to about 10%. The manganese is preferably from about .035 toabout 045%, but may vary from about .005 to about 5%. The percentage ofmagnesium is preferably from about .02 to about .03%, but may vary fromabout .001 to about 2%.

That is, the present preferred alloy is a zinc base alloy containingabout 2.5 to about 3.5% copper; about .25 to about 35% aluminum; about.08 to about 15% silicon; about .035 to about 015% manganese, and about.02 to about 03% magnesium.

Other percentages within the limits given will produce alloys havingimproved physical properties and are useful alloys, but the specificpreferred alloy mentioned appears to have the best physical properties,especially for die casting, and seems to retain these properties withthe least deterioration either by ordinary ageing or by corrosion in thepresence of heat and moisture. Thus, an alloy containing approximately32% aluminum; 2.91% copper; .10% silicon; 023% magnesium; and 04%manganese was found on test to have zero expansion or at least less than.0002 inches expansion on a six inch specimen after exposure to watervapor for ten days at 95 degrees C. The tensile strength as cast wasabout 32,300 pounds per square inch, and after exposure to water vaporand heat for ten days at 95 degrees C. was about 27,530 pounds persquare inch. Elongation as cast was about 1.38% and after exposure asspecified 88%. With the Charpy type of impact test it showed an impactstrength of 31.6 foot pounds per square inch as cast, and after exposureas specified 18.7. It also had good casting characteristics.

As a result of my investigations, I have found that the percenta es ofsilicon substantially as specified in t e zinc base copper alloysproduces an alloy with increased resistance to inter-crystallinecorrosion. The efi'ect of the silicon alone is not as great as when usedwith one or more of the other elements as specified. In other words, ifwe leave out the magnesium, for example, in the specific preferred alloyabove mentioned, we get a desirable alloy with good physical propertiesand small expansion, but by including the magnesium, the properties areimproved still further and the expansion still further reduced orpractically eliminated. It is further'to be noted in all of the abovementioned zinc base copper silicon alloys containing man anese, thatiron, chromium, cobalt and nic el may each be used as a substitute forthe manganese, and would act similarly to the manganese. Investigationsindicate that best results are secured when in the zinc base copperalloy, or zinc base copper aluminum alloy, silicon, manganese, andmagnesium are used, or some of the elements mentioned substituted forthe manganese. I, therefore, Wish it to be understood that in the claimsspecifying manganese with silicon I can substitute iron, chromium,cobalt or nickel in place of the manganese, and intend the claims tocover this.

In effect, the alloys of the invention have good casting properties, lowshrinkage, practically no expansion and corrosion after exposure to heatand moisture, and deteriorate much less in physical properties asmeasured by strength, elongation. and 1mpact value as compared with thenow known zinc base alloys.

Having thus set forth the nature of my invention, what I claim is: g

1. A zinc base alloy containing about 1 to about 15% copper, and about.005 to about 5% silicon.

2. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, and about .005 to about 5% manganese.

3. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, and about .001 to about 2%-magnesium.

4. A zinc base alloy containing about 1 to about 15% copper, about .005to about'5% silicon, and about .005 to about 10% aluminum.

5. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, about .001 to about 2% magnesium and about .005 toabout 5% manganese.

6. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, about .001 to about 2% magnesium and about .005 toabout 10% aluminum.

7. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, about .005 to about 5% manganese, and about .005 toabout 10% aluminum.

8. A zinc base alloy containing about 1 to about 15% copper, about .005to about 5% silicon, about .001 to about 2% magnesium about .005 toabout 5% manganese, an about .005 to about 10% aluminum.

9. A zinc base alloy containing about 1 to about 8% copper, about .025to about .3% silicon, about .01 to about .1% manganese, about .025to-about 1% aluminum and about .01 to about 25% magnesium.

10. A zinc base alloy containing about 1.5 to about 5% copper, about .05to about 20% silicon, about .02 to about .05% manganese, about .05 toabout .50% aluminum and about .01 to about 05% magnesium.

11. A zinc base alloy containing about 2.5 to about 3.5% copper, about0.25 to about 0.35% aluminum, about .08 to about .15%

silicon, about .035 to about 045% manganese, and about .02 to about .03%magnesium.

12. A zinc base alloy containing approximately 3% copper, .30% aluminum,.10% silicon, 025% magnesium, and 04% manganese. Y

In testimony whereof I aflix my signature.

' PASCAL J. MORELL.

